A solid wood door has dimensions- height -2 m- width -0-8 m- thickness -0-04 m- Its thermal conductivity is K -0-04 J s -1 m 1- C -1- The inside air temperature is 20- C and outside air temperature is -10- C- What is the rate of heat flow through the door- assuming the surface temperatures are those of the surrounding air-A- 148 wattsB- 48 wattsC- 408 wattsD- 11-48 watts

The correct option is B 48 wattsdQ/dt=KA(T_2 T_1)/x=0.04 ×(hw)(T_2 T_1)/t^' =0.04 × 2 × 0.8 × [(273+20) (273 10)]/0.04 =48 watts ...

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Byju's Answer

Standard XII

Physics

Convection

A solid wood ...

Question

A solid wood door has dimensions; height = 2m, width = 0.8m, thickness = 0.04m. Its thermal conductivity is $K = 0.04 J s^{- 1} m^{1} (^{\circ} C)^{- 1}$ . The inside air temperature is $20^{\circ} C$ and outside air temperature is $- 10^{\circ} C$ . What is the rate of heat flow through the door, assuming the surface temperatures are those of the surrounding air.

148 watts

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48 watts

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408 watts

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11. 48 watts

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Solution

The correct option is B 48 watts
$\frac{d Q}{d t} = \frac{K A (T_{2} - T_{1})}{x} = \frac{0.04 \times (h w) (T_{2} - T_{1})}{t^{^{'}}} = \frac{0.04 \times 2 \times 0.8 \times [(273 + 20) - (273 - 10)]}{0.04} = 48 w a t t s$

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